The invention relates to the study of the rock formations, through which a borehole passes, by means of recordings as a function of depth, called logs, of certain characteristics measured by probes moved along the borehole.
It is easier to interpret the logs if there is a preliminary operation which involves defining, on the basis of these logs, successive homogeneous rock formation zones along the borehole.
There have already been proposals for various techniques for identifying transitions in a diagraphic recording and for producing the recording in the form of rectangles or crenellations assumed to correspond to strata of geological formations.
More recently, there has been a proposal not to carry out the operation of defining homogeneous zones on the basis of a single log, but to use several logs during this operation. For this purpose, the extent of each homogeneous zone in terms of depth is ascertained by determining, for a series of sampling levels, whether the values of each of the characteristics measured by the various logs used for the definition operation are indeed uniform, that is to say do not differ from one another by an amount greater than a predetermined maximum. This operation thus entails laborious data-processing work.